JP2010089117A - Laser-visual compound sensor for welding, and weld controlling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser-visual compound sensor for welding, which requires only one sensor head and only one measuring system, and to provide a weld controlling method. <P>SOLUTION: The laser-visual compound sensor for welding is used for obtaining a cross-sectional image of a groove that is picked-up by projecting laser light (laser slit light 25) on to the groove, an image of a molten pool directly under an arc, and an image of an electrode 14. In relation to a welding torch 22 as a center, a laser projector 24 is disposed in one of the forward diagonal direction and the rearward diagonal direction relative to the torch moving direction, and an image photographing camera 26 is disposed in the other of the forward diagonal direction and the rearward diagonal direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a welding laser / visual combined sensor using a welding laser sensor and a welding visual sensor in combination, and a welding control method using the welding laser / visual combined sensor.

  Appropriate sensors are indispensable for welding automation. Patent Document 1 discloses a welding visual sensor for that purpose, and Patent Documents 2 to 4 disclose various welding control methods using the visual sensor. The advantage of using a welding visual sensor is that the weld pool and the weld electrode directly above it can be directly imaged during welding, and through that image it can be directly detected whether the position of the weld electrode in the groove is correct. Even if the bending curve of the welding electrode changes, groove tracing control of the welding torch can be accurately performed. In addition, since the change in groove shape can be indirectly estimated in real time, adaptive control of welding conditions can be performed. However, since the molten pool itself is a fluid, it is susceptible to various disturbances, and at the same time, the luminance of the molten pool image is likely to change due to the influence of arc light, so the stability of the molten pool image is not very good. For this reason, it is a disadvantage that the measurement accuracy of the groove dimension change amount cannot be expected to be very high.

  In addition, when there is a tack bead in the groove, even if the visual sensor can detect the presence or absence of the tack bead, generally, when the visual sensor knows, the welding arc has already climbed on the tack bead. Even if the welding conditions can be changed instantaneously at this time, there is a risk that welding defects may remain at the start point and the end point of the tack bead.

  In order to solve the above problems, a method of simultaneously using a welding laser sensor is conceivable. As disclosed in Patent Document 5, a welding laser sensor generally irradiates a groove in front of a welding position with a flying spot laser beam or a slit laser beam, and takes a light-cut image of the groove with a camera. A change in groove shape is directly detected through image processing. Therefore, if an appropriate camera, filter, image processing technique, or the like is used, it is a major feature that satisfactory detection accuracy can be obtained relatively easily. Another advantage of using a laser sensor is that the welding conditions can be achieved with feedforward control. For example, when there is a temporary bead in the groove, the presence or absence of the temporary bead can be detected in advance by the laser sensor, so that the welding conditions are changed in a timely manner when the arc passes through the temporary bead. Therefore, welding can be performed without leaving a welding defect at the start point and the end point of the tack bead.

  Laser welding sensors are often used for groove profile control, but there is a drawback that it is difficult to use in curve groove profile control because there is a time lag between measurement and control. Further, even in the case of straight groove tracking control, it is necessary that the relative position between the welding electrode and the laser sensor is fixed or the change amount thereof can be grasped in real time. This is because the laser sensor cannot measure the relative position between the sensor and the electrode in real time because the welding electrode is not in the field of view. Therefore, if there is a random variation in the relative position between the sensor and the electrode, the amount of change remains as an error in groove tracking control.

  As described above, it can be seen that welding visual sensors and laser sensors have their respective strengths and weaknesses. Therefore, if both are used simultaneously, an ideal welding control system that can complement each other can be constructed.

JP 2006-7303 A JP 2006-55858 A JP 2006-281282 A JP 2007-185700 A JP 2002-120066 A

  However, if both are used at the same time, two sensor systems are required, which is expensive, and at the same time two sensor heads must be mounted in the vicinity of the welding torch. There is a risk of significantly impairing accessibility.

  Accordingly, an object of the present invention is to provide a welding laser / visual sensor and a welding control method that require only one sensor head and one measuring system in order to solve the above-described problems.

  The present invention is a welding laser / visual composite sensor for obtaining a groove cross-sectional image of a laser beam projected on a groove, and an image of a molten pool and an electrode directly under the arc, with a welding torch as the center, The above-mentioned problem is solved by arranging a laser projector in one of the forward and backward oblique directions of the torch moving direction and an image taking camera in the other.

  Here, the sum of the irradiation angle of the laser beam by the laser projector and the shooting angle by the image shooting camera can be 90 °.

  In the present invention, the welding laser / visual composite sensor is used to move the welding torch while projecting the laser projector onto the groove at the time of non-welding. The present invention provides a welding control method characterized in that a cross-sectional image is photographed, a weld pool and an electrode directly under an arc are photographed by an image photographing camera during welding, and the obtained information is used for welding control.

  In the present invention, first, with the welding torch as the center, the camera of the photographing means is arranged in the diagonally forward direction of the torch moving direction, and the laser projector of the illuminating means is arranged on the opposite side of the torch. Of course, the installation positions of the camera and the laser projector may be reversed. Then, at the time of non-welding, this system can function as a laser sensor. That is, the torch is moved while projecting the laser projector obliquely onto the groove. At this time, a groove cut image of the laser beam is taken with a camera on the opposite side of the torch. If the obtained groove light section image is subjected to image processing, shape information such as the upper and lower widths (gap) and depth of the groove can be obtained. At the same time, it is possible to know torch position information such as the groove center position and torch height (distance to the groove surface) during measurement. Based on this position information, the torch left-right position and height control during measurement is performed, and if the control trajectory result is stored together with the groove shape information, the groove required for the welding control device during welding is stored. It is also possible to provide reproduction control data for copying and torch height copying.

  On the other hand, during welding, the camera takes a picture of the molten pool and the electrode directly under the arc. This is a usage as a so-called visual sensor. If the captured image is image-processed, it is possible to measure whether the groove tracing state of the torch and the amount of welding in the groove are optimum. If it is determined to be inappropriate, it can be immediately corrected through the feedback control method.

  In general, the laser projector is not irradiated during welding, but irradiation can be performed as necessary.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a configuration example of a laser / visual composite sensor of the present invention as a laser sensor. Here, the welding torch 22, the laser projector 24, and the image capturing camera 26 are all attached to the same holder 20. The reason for this is to keep the three people always taking the same movement and eliminating relative movement. In addition, a filter set 28 is provided in front of the image capturing camera 26, and a laser sensor filter 30 and a visual sensor filter 32 are respectively installed therein, and an appropriate optical filter is provided for the sensor according to the application. In the figure, 10 is a workpiece, 12 is a welding head, and 14 is a welding electrode.

  FIG. 2 is a schematic diagram of a groove cut image of the laser slit light 25 photographed by the image photographing camera 26. This is an example of a laser beam cut image of a V-shaped groove, but if this image is processed, the point positions of SP1 to SP5 called singular points can be found. Then, SV1 to SV8 called feature amounts are obtained from these singular points. Here, SV1 represents a groove width and SV2 represents a root gap. However, as can be seen from FIG. 1, the laser slit light 25 is not orthogonal to the workpiece 10 that is the object to be irradiated but intersects obliquely, and thus the obtained singular points SP1 to SP5 are in the same cross section. is not. This situation is shown in FIG. Therefore, when there is no difference, the values of SV1 and SV2 can represent the groove width and the root gap themselves, but when there is a difference, it can be understood that they can only be expressed approximately. This error becomes smaller as the irradiation angle α of the laser slit light 25 is smaller.

  On the other hand, the values of SV3 to SV8 are incorrect, SV4 and SV5 represent the left and right gaps of the backing, SV6 and SV7 represent the left and right plate thicknesses, and SV8 represents the groove depth. For the same reason as above, these can also be represented only by approximate values. Similarly, the smaller the irradiation angle α of the laser slit light 25, the closer to the true thickness and depth. Further, in order to make the resolution of the parameters representing the thickness, depth, and the like as uniform as possible in the image capturing camera 26, there is a residual relationship between the capturing angle β by the image capturing camera 26 and the irradiation angle α of the laser slit light 25. It is desirable to have it.

  The reason is that if the sum of α and β is not 90 ° as shown in FIG. 4, the image formed on the camera is theoretically as if the virtual image of the subject was seen, so see FIG. 4. Thus, even if the subject has the same length on both the upper and lower sides around the lens optical axis, the virtual image has a different length on both the upper and lower sides around the lens optical axis. This is because the lengths of the upper and lower sides around the axis (screen) are also different. This difference becomes smaller as the sum of α and β approaches 90 °.

  Further, the center position of the groove is obtained from SP1 and SP2 or from SP3 and SP4 as can be seen from FIG.

  FIG. 5 is a schematic diagram of a laser beam cut image of the temporary bead portion in the groove. Here, similarly, five singular points SP1 to SP5 are obtained. Therefore, if SV1 to SV8 of the feature amount are obtained from these and the feature amounts of the groove without the temporary bead are compared, it can be determined whether or not it is a temporary bead. For example, one feature of the temporary bead portion is that the groove depth SV8 is shorter than the plate thickness.

  FIG. 6 shows the measurement flow of this embodiment. The left side is a measurement flow when using a laser sensor, and the right side is a measurement flow when using a visual sensor. The selection can be made by changing the measurement mode before use (step 102).

  On the other hand, FIG. 7 shows a configuration example when used as a visual sensor of the composite sensor. In the figure, 16 is a welding arc.

  Here, the difference from the case where it is used as a laser sensor is that laser irradiation is not required and a visual sensor filter 32 is installed in front of the image capturing camera 26. The filter replacement operation can be easily realized by rotating the filter set 28 by 90 °. This operation can be performed automatically using an electromagnet or the like, or can be performed manually. If the wavelength of the laser sensor filter 30 and that of the visual sensor filter 32 can be made the same, the replacement work of this filter becomes unnecessary and the structure becomes simple.

  As the visual sensor measurement method during welding, those described in Patent Documents 2 to 4 can be used.

  On the other hand, FIG. 8 shows an example of a welding control method based on respective information of the laser sensor and the visual sensor.

  Here, the welding control is first performed by the teaching playback method based on the data information obtained by the laser sensor. This control is mainly adaptive control of welding conditions, that is, welding conditions based on the presence or absence of a temporary bead in the groove, the groove width, the groove depth, the root gap, and the like for each welding position. A control correction amount (such as welding current, voltage, welding speed, torch swing width, swing end stop time) is obtained, and these are added to the reference welding conditions for welding.

  It is possible to follow the groove of the welding torch based on the groove width obtained from the laser sensor and the center position data of the root gap, but the actual deviation of the scanning control is further reflected in the data information obtained by the visual sensor during welding. Modify based on.

  Therefore, the visual sensor is mainly used for groove tracking control of the welding torch. However, during the first layer welding, because there are fluctuations in the gap of the backing and changes in the amount of molten metal that has entered the gap, just teaching playback control based on the data information obtained by the laser sensor before welding, It can be difficult to maintain a high quality first layer weld bead. Therefore, based on the height of the weld pool at the time of the first layer welding obtained from the visual sensor (see Patent Documents 3 and 4), an additional correction amount of the welding amount is obtained, and in addition to the teaching playback data, welding is performed. Control can also be performed.

  Also, in case of emergency, manual control is added from the remote control at hand. For example, manual correction can be added in-process when an emergency stop is detected or a control deviation is detected from the monitor.

  As a result of the welding control based on the above combined laser and visual sensor, it is possible to achieve full automation of the welding process, and at the same time, even if the actual groove shape deviates greatly from the standard shape, for example, steel plate backing In the case of a groove with a mark, it was confirmed that a uniform and high-quality weld bead can be obtained regardless of whether the root gap fluctuates from 2 mm to 12 mm and whether or not a temporary bead is present.

  In the embodiment, the laser slit light is irradiated from the laser projector. However, the method of obtaining the light cut image is not limited to this, and for example, the flying spot light may be irradiated.

The perspective view which shows the use condition as a laser sensor of embodiment of the laser-visual compound sensor which concerns on this invention Similarly, a schematic diagram of a laser beam cut image of a V-shaped groove Similarly, a schematic diagram of a laser slit light cut image viewed from the welding torch direction Similarly, the effect of the sum of the irradiation angle α and the shooting angle β on the uniformity of resolution Similarly, a schematic diagram of a laser beam cut image of a temporary bead Flow chart showing a measurement procedure using the embodiment The perspective view which shows the use condition as a visual sensor of the said embodiment. The figure which shows the method of the welding control using the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... To-be-welded object 12 ... Welding head 14 ... Welding electrode 16 ... Welding arc 20 ... Holder 22 ... Welding torch 24 ... Laser projector 25 ... Laser slit light 26 ... Imaging camera 28 ... Filter set 30 ... Laser sensor filter 32 ... Filter for visual sensor

Claims (3)

A welding laser / visual composite sensor for obtaining a groove cross-sectional image of the laser light projected on the groove, and an image of the weld pool and electrode directly under the arc,
A laser / visual composite sensor for welding characterized in that a laser projector is disposed in one of the forward and backward oblique directions of the torch moving direction centering on the welding torch and an image photographing camera is disposed on the other.   2. The combined laser / visual sensor for welding according to claim 1, wherein a sum of an irradiation angle of the laser beam by the laser projector and an imaging angle by the image capturing camera is 90 °. Using the welding laser / visual composite sensor according to claim 1 or 2,
At the time of non-welding, move the welding torch while projecting the laser projector onto the groove, and take a cross-sectional image of the laser light with the image camera.
During welding, we photograph the molten pool and electrode directly under the arc with an image camera.
A welding control method, wherein the obtained information is used for welding control.

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